Support craft perform a vital role in assisting with safe operations and emergency response for liquefied gas carriers and facilities. The effectiveness of this service could be improved by a more up-to-date approach and an improved understanding of the hazards, barriers, credible scenarios and credible response strategies.

The information in this book is provided primarily for organisations involved in the transportation of liquefied gas cargoes, including support craft, facilities and ships. It may also be of assistance to regulators and government agencies. Suggested competency standards have been provided at Annex D to assist with the creation of training programmes for the crew of support craft.

iii CONTENTS PART 1 Scope and Methodology ...........................................................................................................................1 1. Introduction ......................................................................................................................................................3 1.1 Introduction ..............................................................................................................................................5 1.2 Scope ......................................................................................................................................................6 1.3 Risk Based Method and Terminology ..........................................................................................................7 1.4 Document Structure .................................................................................................................................10 PART 2 Assessing the Risk and the Management of Specific Events .......................................................................11 2. The Operating Environment .............................................................................................................................13 3. Top Events ......................................................................................................................................................17 3.1 Loss of Containment ................................................................................................................................21 3.2 Collision/Grounding ...............................................................................................................................34 3.3 Loss of Position .......................................................................................................................................40 3.4 Intrusion.................................................................................................................................................44 Annexes ...............................................................................................................................................................45 Annex A – Response Considerations and Planning .............................................................................................47 Annex B – Equipment and Capabilities of Support Craft ......................................................................................51 Annex C – Water-spray Systems .......................................................................................................................57 Annex D – Support Craft Emergency Response Competencies ............................................................................59 Annex E – Fire and Gas Dispersion Modelling ...................................................................................................80 Annex F – Properties of Liquefied Gases ............................................................................................................83 Annex G – Glossary of Terms and Abbreviations ................................................................................................85 Annex H – References ......................................................................................................................................87 5 Introduction 1. Introduction 1.1 Introduction Support craft perform a vital role in assisting with safe operations and emergency response for liquefied gas carriers and facilities. The effectiveness of this service, provided by support craft, could be improved by a more up to date approach and an improved understanding of the hazards, barriers, credible scenarios and credible response strategies. The information in this document is provided primarily for organisations involved in the transportation of liquefied gas cargoes, including support craft, facilities and ships. It may also be of assistance to regulators and government agencies. Suggested competency standards have been provided at Annex D to assist with the creation of training programmes for the crew of support craft. Figure 1.1: Support craft (Courtesy Smit Lamnalco) This document uses a risk assessment method and terminology, which is discussed in Section 1.3, to explain the environment and define some example scenarios and response strategies. All of the responses contained in this document are based on the following order of priority: protection of life, the environment and property. Protection of life has been considered not only in the context of the ship and terminal staff involved in a cargo operation, but also in the context of the emergency responders and the general public in the vicinity. Evaluating a top event without understanding the design barriers built in to reduce risk may lead to an improbable conclusion being reached. SIGTTO is of the opinion that knowledge of the design basis for facilities and gas carriers, including typical credible (design) scenarios, may assist in the improvement of existing practice. This document therefore sets out to increase awareness of the philosophy behind the design, including the purpose and limitation, of equipment used. Appreciation of the credible scenarios should also assist the industry in carrying out more effective drills and exercises. The Annexes contain further information that may assist with improving emergency response. Based on the range of scenarios a support craft could encounter, the suggested competency standards provided at Annex D may assist with the effectiveness of the response strategy. Relevant information is provided about the equipment used in emergency response and its effectiveness. Readers are also encouraged to refer to the publications listed in the References, as they may provide further relevant information. SIGTTO acknowledges that its ability to provide effective guidance is the result of industry wide consultations. We welcome any comments or suggestions for improvements that could be considered for inclusion in future editions. 6 1.2 Scope This document provides information for support craft on emergency response strategy to major incidents. This includes ISPS and guard zone duties, but not to normal operations such as berthing and unberthing or responses to minor incidents and occupational safety incidents. It is not possible to dictate exactly what should be done in an emergency as every circumstance will be different, so this document only considers a few typical scenarios. All of the scenarios discussed are based on typical and credible incidents that may occur during the operation of a liquefied gas carrier within the limits of a facility, ie when approaching, departing or alongside the berth. They do not apply to situations where the gas carrier is beyond the effective range and jurisdiction of a port or a liquefied gas terminal’s response plan. This document is only applicable to liquefied gas facilities that handle liquefied natural gas (LNG) and liquefied petroleum gas (LPG). Chemical gases, such as ammonia, butadiene and vinyl chloride monomer (VCM), require additional measures due to the hazards of toxicity and pollution and so are not covered in the scope of this document. However, the general approach taken may be helpful when formulating a response strategy. This document covers onshore facilities (including near shore FSRU). Offshore facilities (including FLNG and offshore FSRU) are covered in the second of this series of documents. This document does not cover ship to ship transfer operations (Refer to STS Guide, Reference 4). Figure 1.2: Liquefied gas terminal (Courtesy Smit Lamnalco) Figure 1.3: FSRU terminal (Courtesy Excelerate Energy) Introduction 7 Introduction 1.3 Risk Based Method and Terminology A risk assessment is a systematic process of evaluating the potential risks that may be involved in a planned activity or undertaking. Risk assessment is a proven method to manage hazards in a structured manner. This document adopts risk assessment terminology, and tools such as the ‘bowtie method’, to present the information in a logical and sequential manner (see 1.3.1). This document uses the bowtie method to highlight potential and plausible events, the possible causes and the barriers that are typically in place to prevent such an event occurring. This leads to analysis of the consequences of the event and what may already be in place to reduce them. The response and protection strategies suggested for support craft are based on this approach. It is important to note that while this document adopts a particular style of a risk assessment terminology, the information contained does not constitute a formal risk assessment. Only a few selected cases have been considered and a full risk assessment should be carried out for each facility to identify the relevant risks and barriers that may be needed. 1.3.1 The ‘Bowtie’ Method of Risk Assessment and Management While the bowtie methodology is generally used as part of a risk assessment and risk management process, this document uses its visual presentation feature - the bowtie diagram. One of the strengths of the bowtie diagram is that it provides a simple and unambiguous overview of a situation where risks have been identified. Hazards For the purposes of this document, a hazard is the property of a ‘dangerous substance’ or a ‘physical situation’ with a potential for creating damage to human health and/or environment and property. When liquefied gas is contained within tanks and pipelines it is safe and poses no risk, ie it is a stable cargo that does not polymerise or decompose to form an unstable substance. It is only in the event of a loss of containment that liquefied gas becomes a hazard. This is why gas carriers and facilities have design considerations to guard against loss of containment. The main hazard of LPG and LNG vapour is that it is flammable. The additional hazards of LNG and LPG are the low temperature and pressures at which they may be carried. LPG may be carried at ambient temperature in pressure tanks, but LNG is always carried at low temperatures, even in pressure tanks, as it does not remain as a liquid at ambient temperatures. The main ‘dangerous substance’, related to the operation of liquefied gas carriers, is the cargo carried. This document considers the hazards of propane, butane and methane, carried in liquefied form on gas carriers. These may be carried in pressurized or atmospheric pressure tanks. The ‘physical situation’ is the operation of gas carriers while in port, including in the approaches to the port, in departing and arriving at the port and during the period alongside the berth. These hazards could lead to damage of the gas carrier and jetty and may also result in the release of liquefied gas. A gas carrier is exposed to the same operational risks as any other ship of similar size when operating in port areas. However, the consequences of severe structural damage to a gas carrier may be far more serious than for similar incidents involving other ship types. Every aspect of the operation of gas carriers in port areas, including the location of holding anchorages, the transit to and from sea, the location of the berth and the management of other marine traffic while the ship is alongside the berth, requires careful analysis and detailed planning to eliminate any credible probability of the ship sustaining serious structural damage. 8 Introduction Hazard Proactive Barrier Proactive barriers prevent the ‘top event’ from occurring. For example, high pressure alarms are a proactive barrier to prevent overpressure from resulting in a loss of containment. Reactive Barrier Reactive barriers prevent the consequence from occurring. For example, restriction on ignition sources prevent loss of containment from ignition. Threats Threats are the factors that have the ability to cause a ‘top event’. For example, overpressure could lead to a release of propane vapour from a cargo containment system. Top Event A ‘top event’ occurs when the hazard is no longer safely contained and there is potential for an incident. For example, loss of containment of propane from a cargo containment system is a likely event that could result in an incident. Consequences Consequences are potential events that could result from a ‘top event’. For example, ignition of propane vapour that has been released from a cargo containment system. Figure 1.4: Bowtie diagram The bowtie method qualifies risk by showing the relationship between hazards, top events (events that could happen), threats (possible causes) and consequences (effects). Barriers are measures taken to prevent certain events from happening. Sometimes the barriers are referred to as ‘controls’, but in this document we use the term barrier. Hydrocarbon (LPG) The Hazard Loss of Containment Top Event High Pressure Alarms Proactive Barrier Restriction on Ignition Sources Reactive Barrier Overpressure Threat Ignited Release Consequence Figure 1.5: Simplified bowtie for loss of containment 24 Top Events Figure 3.6 shows a dispersion model for a drip tray with liquid methane. This could occur at the manifold area of a ship following a leak from a loading arm. In this case an instantaneous model is used as the entire amount vaporises in 1 minute (on land). 0-1001002003000 -20 -40 -60 -80 20 40 60 80 Downwind Distance (m) Height (m) 24 s 48 s 72 s 96 s 120 s 144 s Material : Methane Time of Interest Wind Speed : 5 m/s Stability Category : DConc is 53% vol/vol Figure 3.6: Dispersion of methane Figure 3.7 shows a similar dispersion model for a drip tray with liquid propane. Downwind Distance (m) Height (m) 5010015020000 -20 -40 20 40 -50 15 s 30 s 45 s 60 s 75 s 90 s Material : Propane Time of Interest Wind Speed : 5 m/s Stability Category : DConc is 2.1% vol/vol Figure 3.7: Dispersion of propane These dispersion models provide only a general indication of what may occur. When planning response strategies for support craft, models specific to the facility should be considered. Dispersion models show that it takes only a small amount of time for small quantities of liquefied gas to evaporate and dissipate. Therefore, support craft may not be able to provide an effective response for small quantities due to the time it would take them to reach a suitable position. Dispersion models are also helpful in providing support craft with a general awareness of the direction and extent of a flammable cloud. This could assist the Master of a support craft (which could be a source of ignition) in staying well clear of a vapour cloud. 27 Top Events Test Button High HighFloat High Cargo tank dome shell Figure 3.9: Typical high level alarm that can be tested 3.1.3 Consequences and Barriers Hydrocarbon (LNG/LPG) Loss of Containment Spilldrains to bunded areasTerminal locationConstant monitoring Space for crew protected from cargo vapour Trained teams for isolation with PPEGas detectionLocation of air intakes Emergencyshutdown of valvesand machinery Unignited release Space for crew protected from fire Trained multiple fire teams with PPE Fusible plugs automatically initiate shutdown Activefire protection water spray system) Location of vent mastsDesign of ventilationRestriction on ignition sources Refer to unignited release barriers Ignited release Constant monitoringWater curtain at manifold area (LNG)Drip trays Ship structure design considerations Cold spill Figure 3.10: Selection of generic consequences and barriers for loss of containment Consequence – Unignited release An unignited release of vapour has the potential to ignite or cause asphyxiation. However, LNG and LPG vapours are not considered to be toxic. Small leaks from pump glands, valves, pipe flanges or from vent risers may initially produce vapour. This vapour should not ignite spontaneously but, if the escape is large, there may be a risk of the vapour cloud spreading to a source of ignition. A release of gas in liquid form usually causes the formation of a vapour cloud that travels horizontally from the spill point under the influence of prevailing wind. As it travels away from the spill point it becomes less dense and should start to disperse. Once a gas cloud is no longer fed by fresh volumes of gas it should disperse into the atmosphere and be diluted to below its lower flammable limit (LFL).